The common feature of vasogenic, interstitial and late ischemic brain edema is an increase in the extracellular fluid space volume. Bulk fluid movement through the brain has been proposed as one mechanism of edema resolution. We plan to study the biomechanics of such bulk flow characterizing the attendant changes in tissue properties. Controlled edema volumes will be induced in the brain to study the effect of edema on local CBF and CBF control, the effect of edema on intracranial biomechanics, the routes of bulk flow, and any selective vulnerability of edematous tissue to ischemia. Knowledge of brain edema dynamics should suggest new approaches to therapy.